The present invention generally relates to combustible materials. More particularly, the present invention relates to chemically treating combustible materials prior to combustion.
Briefly described, the present invention is a method of treatment of combustible materials with sodium silicate prior to combustion. The preferred combustible material is coal or lignite, and most preferably stoker coal. Sodium silicate is applied in aqueous form, preferably by spraying, to the coal to at least form a partial coating around the individual particles of coal. The treated coal is then preferably combusted in the burn chamber of a coal-fired boiler and has greatly reduced pollutant emissions.
The coating of sodium silicate greatly reduces particulate emissions, smoke, benzo-A-pyrene, and other noxious emissions. Dependent on the thickness and amount of sodium silicate applied to each individual piece of coal, noxious emissions can be reduced up to 100 times less than normal. Additionally, the water present in the aqueous sodium silicate significantly increases the boiler efficiency by increasing the combustion efficiency of the treated coal.
An object of the present invention is to provide a method of pretreating combustible materials which greatly reduces pollution emission when the materials are combusted.
Another object of the present invention is to provide a method of pretreating combustible materials which greatly enhances combustion efficiency when the materials are combusted.
Another object of the present invention is a fuel combustion process resulting in reduced pollution emission and enhanced combustion efficiency.
A further object of the present invention is to provide a treated fuel for combustion in a furnace.
Other objects, features, and advantages of the present invention will become apparent after review of the hereinafter set forth Detailed Description of the Invention.
The present invention is a method of treating combustible materials, preferably coal or lignite, and most preferably stoker coal, prior to combustion in a furnace or boiler. In the preferred embodiment, stoker coal is subjected to a spray of aqueous sodium silicate upon the individual particles of the stoker coal prior to combustion in a coal-fired boiler. While the present method of treatment can be used on stoker coal of any size, it is preferred that the coals which are to be subject to the aqueous sodium silicate spray be no smaller than 20 mesh.
The application of sodium silicate to the stoker coal causes at least a partial coating to form therearound. Sodium silicate (such as Na2Si4O9 or Na2SiO3) is a generic term for a family of chemicals comprised of sodium oxide (Na2O), silica (SiO2), and typically water (H2O). Commercial grades of sodium silicate are readily available and fairly inexpensive. For purposes of the present invention, the preferred sodium silicate is xe2x80x9cKxe2x80x9d brand sodium silicate from the PQ Corporation. The data sheet (Exhibit A) and analysis certificate (Exhibit B) for K brand sodium silicate are attached hereto and incorporated herein by this reference. The concentration of sodium silicate in the aqueous form is preferably altered from the commercial concentration disclosed in the data sheet depending on final concentration and effect desired. However, the sodium silicate is preferably mixed to a maximum percentage of 10% sodium silicate by weight with neutral to slightly acidic water.
The sodium silicate is sprayed on the stoker coal briquettes in an amount ranging from 35 ft2/gal to 250 ft2/gal depending on porosity and size of the coal, and amount of coating desired. The square footage for spraying is determined mathematically from the size, shape, and volume of the combustible coal. To provide a thorough coating, 35 ft2/gal will substantially cover the individual stoker coal particles to preferably form a solid coating therearound upon drying. While a minimal spray, e.g. 250 ft2 or greater per gallon will sparsely cover the individual stoker coal particles, even such minimal coating still has value in reduction of pollutant emissions during combustion and enhanced physical burning characteristics.